llms.txt end points for each doc route

# Feature request
It would be great with all the lllm / context related type things going on if each route for a document would also expose a /llms.txt equiv route.

## Summary
Can we implement llmstxt endpoints for documentation. here is a link to an example and further explanation of what llmstxt is https://llmstxt.org/

## Examples

https://context7.com/openai/openai-agents-python/llms.txt